1. Field of the Invention
This invention relates generally to the formation of metal films, and more particularly, to a method for forming a porous platinum film suitable for use in applications such as electrodes.
2. Description of the Related Art
Metal films, such as platinum films, are commonly used as electrodes in a variety of applications, including, fuel cells, batteries, and sensors. In such metal electrodes, it is desirable for the electrodes to have high specific surface areas to increase efficiency and reduce size. The specific surface area of the electrode increases as the porosity of the film used to form the electrode increases.
One current technique for forming porous platinum electrodes is directed to controlling electrodeposition parameters during a plating operation. Due to the number of processing steps, this technique is difficult to control, costly, and also requires that the substrate over which the electrode is formed be conductive.
Another technique involves the formation of a lattice and the deposition of a liquid containing a platinum salt within the windows of the lattice (Attard et al. Oct. 31, 1997. Mesopourous Platinum Films from Lyotropic Liquid Crystalline Phases. Science, 278, 838-840.). The platinum salt is subsequently reduced electrochemically, and the lattice is removed by extensive washing. Lyotropic crystals generated from surfactants exhibit long range periodicities with repeat distances from 2 to 15 nanometers. The electrochemical reduction of the platinum salts confined to the aqueous environments of these phases leads to the deposition of platinum films that have a long range porous structure and high specific surface area. This technique also requires a conductive substrate to perform the electrochemical reduction of the platinum salts, and is costly due to the number of processing steps involved.
Although the techniques described above are suitable for forming electrode surfaces, they are relatively costly and require a multitude of processing steps, thus making them more difficult to control. Also, because these techniques require the presence of a conductive substrate, their range of potential applications is correspondingly limited.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.